This invention relates to the field of trays for storing and transporting bakery goods and the like and particularly to the field of such trays which may be nested one within the other for storing in an empty condition but may be stacked one upon another when the trays are full of bakery goods.
There are in the prior art innumerable unitary plastic trays which are both nestable and stackable. Additionally, there are numerous such trays which may be stacked one upon the other when the trays are similarly oriented and which may be nested one within the other when the trays are rotated 90.degree.. One such tray of this latter type is illustrated in Bockenstette U.S. Pat. No. 3,392,875.
All of the molded plastic trays which have open gridwork bottom walls made from a gridwork of intersecting ribs tend to bow in the center when loaded heavily because of the lack of rigidity of the rib-defining gridwork. Additionally, trays of the type shown in the Bockenstette patent which have long low profile side walls and relatively shorter high profile end walls lack sufficient rigidity to resist torsional flexure if the tray is unevenly loaded.
Accordingly, it has been a primary objective of this invention to provide a unitary molded plastic tray which has a long low profile side wall and high profile end walls as well as an open gridwork bottom structure but which has a very rigid bottom which better resists bowing and torsional deflection than prior art trays.
This objective is accomplished and this invention is predicated upon the discovery that a unitary molded plastic tray which has an open gridwork bottom structure defined by intersecting ribs and which has a pair of high profile end walls and low profile side walls may be made much more rigid than prior art trays if the ribs which form the bottom gridwork are generally T-shaped in cross section and extend diagonally across the side and end walls so that the ribs form an acute angle of approximately 45.degree. with the side and end walls. This structure results in a tray in which the bottom better resists bowing under heavily loaded conditions as well as torsional flexing when the tray is unevenly loaded or is twisted between handles in the end walls.
The primary advantage of the tray of this invention is that it provides a more rigid structure without requiring any greater quantity of material and without requiring that the tray be made from different material than prior art trays.